Diabetes mellitus is a disease in which cells fail to uptake glucose either due to a lack of insulin (Type I) or an insensitivity to insulin (Type II). The associated elevation of blood glucose levels for prolonged periods of time has been linked to a number of problems including retinopathy, nephropathy, neuropathy, and heart disease. A typical care regimen for Type I diabetics includes daily monitoring of blood glucose levels and injection of an appropriate dose of insulin. Conventional glucose monitoring involves the use of an invasive “finger-stick” method in which the finger of a subject is pricked in order to withdraw a small amount of blood for testing in a diabetes monitoring kit based on the electroenzymatic oxidation of glucose.
Fluorescence is a photochemical phenomenon in which a photon of specific light wavelength (excitation wavelength) strikes an indicator (fluorophore) molecule, thereby exciting an electron to a higher energy state. As that “excited” electron decays back down to its original ground state, another photon of light is released at a longer wavelength (emission wavelength).
Fluorescence resonance energy transfer (FRET) involves the transfer of non-photonic energy from an excited fluorophore (the donor) to another fluorophore (the acceptor) when the donor and acceptor molecules are in close proximity to each other. FRET enables the determination of the relative proximity of the molecules for investigating, for example, molecular interactions between two protein partners, structural changes within one molecule, ion concentrations, and the binding of analytes.